76 lines
1.8 KiB
C
76 lines
1.8 KiB
C
/*
|
|
* Program to calculate mersenne primes
|
|
* using Lucas-Lehmer test - Knuth p.391
|
|
*
|
|
* Try this only in a 32-bit (or better!) environment
|
|
*
|
|
*/
|
|
|
|
#include <stdio.h>
|
|
#include "miracl.h"
|
|
#define LIMIT 100000
|
|
|
|
int main()
|
|
{ /* calculate mersenne primes */
|
|
BOOL compo;
|
|
big L,m,T;
|
|
int i,k,q,p,r;
|
|
miracl *mip=mirsys(5000,0);
|
|
L=mirvar(0);
|
|
m=mirvar(0);
|
|
T=mirvar(0);
|
|
gprime(LIMIT);
|
|
for (k=1;;k++)
|
|
{ /* test only prime exponents */
|
|
q=mip->PRIMES[k];
|
|
if (q==0) break;
|
|
expb2(q,m);
|
|
decr(m,1,m); /* m=2^q-1 */
|
|
|
|
/* try to find a factor. Should perhaps keep trying over a bigger range... */
|
|
|
|
compo=FALSE;
|
|
for(i=2;i<16*q;i+=2)
|
|
{ /* prime factors (if they exist) are always *
|
|
* of the form i*q+1, and 1 or 7 mod 8 */
|
|
p=i*q+1;
|
|
if ((p-1)%q!=0) break; /* check for overflow */
|
|
if (p%8!=1 && p%8!=7) continue;
|
|
if (spmd(3,p-1,p)!=1) continue; /* check for prime p */
|
|
|
|
r=subdiv(m,p,T);
|
|
if (r==0)
|
|
{
|
|
if (size(T)!=1) compo=TRUE;
|
|
break;
|
|
}
|
|
}
|
|
if (compo)
|
|
{
|
|
printf("2^%d-1 is NOT prime ; factor = %7d\n",q,p);
|
|
continue;
|
|
}
|
|
|
|
convert(4,L);
|
|
for(i=1;i<=q-2;i++)
|
|
{ /* Lucas-Lehmer test */
|
|
fft_mult(L,L,L);
|
|
decr(L,2,L);
|
|
|
|
sftbit(L,-q,T);
|
|
add(L,T,L);
|
|
sftbit(T,q,T);
|
|
subtract(L,T,L);
|
|
if (mr_compare(L,m)>=0) subtract(L,m,L);
|
|
}
|
|
if (size(L)==0)
|
|
{ /* mersenne prime found! */
|
|
printf("2^%d-1 is prime = \n",q);
|
|
cotnum(m,stdout);
|
|
}
|
|
else printf("2^%d-1 is NOT prime\n",q);
|
|
}
|
|
return 0;
|
|
}
|
|
|